Abstract

Toward obtaining it more detailed understanding of the influence of SOx poisoning oil the mechanism of NOx uptake on a NOx storage and reduction (NSR) catalyst, we have performed a model Study under ultrahigh vacuum (UHV) conditions. A Supported model catalyst based oil a thin well-ordered alumina film grown oil a NiAl(110) single crystal is used Onto which BaO and Pd particles are deposited. Time-resolved (TR) infrared reflection absorption spectroscopy (IRAS) is applied to identify the species formed during NO2 uptake on the catalyst surface, which has been pretreated with SO2. These results are compared to the NO2 uptake on the corresponding fresh samples.It is shown that SO2 readily decomposes upon adsorption oil both the pristine Al2O3 surface and the BaO and Pd loaded model systems. NO2 reoxidizes the decomposition products 10 surface sulfites and sulfates. A pronounced influence of the SO2 species oil the interaction with NO2 is observed leading to reduced NO2 uptake and to a change of the preferential adsorption geometry from bridging to monodentate. A comparison of the integral intensity of the nitrate bands oil the Ba-free and the Ba-containing samples Furthermore Suggests that SO2 adsorbs preferentially on Ba2+ centers rather than oil the Al3+ centers.